Type II collagen pro-alpha-chains containing a Gly574Ser mutation are not incorporated into the cartilage matrix of...

The biochemical consequences of a type II procollagen mutation that contained a Gly574Ser amino acid substitution were analyzed in a transgenic mouse strain. The mutation correlated with one previously characterized in a patient with the lethal human chondrodysplasia, hypochondrogenesis (Horton et al., 1992), and resulted in a similar shortlimbed phenotype. There were fewer collagen fibrils present in the transgenic cartilage and reduced immunofluorescence of cartilage matrix using a type II collagen antibody. Pepsin-extracted collagen from transgenic mouse embryo cartilage was analyzed electrophoretically and indicated less type II as well as type XI collagen compared to their wild-type littermates. A pulse-chase experiment was performed to evaluate the biosynthesis and fate of type II collagen. Chondrocytes isolated from transgenic tissue synthesized fewer stable molecules, resulting in decreased secretion of the procollagen chains. By amino acid sequence analysis of the type II collagen peptides from cartilage of transgenic mouse embryos, serine was not detected at residue 574, the site mutated in the transgene. Based on sequence data, we believe that the molecules incorporated into collagen fibrils of the extracellular matrix, while fewer in number, were composed of normal alpha 1(II) chains.